very strange speaker problem

I just purchased and installed new speakers (alpine sps 170A). Previously, i had no speakers connected to my head unit, which is a new(ish) sony mp3 cd player. I installed the speakers myself, and they worked for a while. Yesterday, i got into my car and i started the engine, when i did, my right speaker (only the right, and not the left) made a humming sound. I found this strange, yet the speakers still worked and sounded fine, although every once in a while, i would hear the humming sound, and the right speaker would fade out for a few seconds. This problem continued and actually worsened. Now whenever i get into my car, when i turn the engine on, the right speaker humms for a few seconds, and then when the music comes on, it remains silent. When i turn off my car, it also humms in the exact same fashion. When it humms, no music comes through the other speakers. I dont believe the humming is causing the other speakers not to play music, i think that music is not normally played when the humming occurs, that is... the humming happens when the amp has just been turned on, and when it is shutting down.i dont think it is the speaker because its so new, and the amp is stil; quite new as well. I checked the connections on the speaker today and they are all apparently good, i even soldered the wires on.

it almost sounds like you might not have a good connection on your speakers. Are you positive that the connections are solid? Did you solder them? Are they butt-end connectors? Are they twisted together and then a cap put on them? Did you utilize the factory speaker wire from the head unit to the speaker? Do you have a factory amp in this car? what kind of car is it?

You say that previously you didn't have any speakers connected to this head unit...is that to say that you simply didn't have any speakers in your car at all or that they were going through an amp previously?

If you can play no sound at all, turn the system up, does the humming increase? If so that is a nosie problem playing in with other power lines in your car. All you did was replace speakers so it shouldn't be an issue. What's the Head Unit and speakers you have in and the car you have? So we can know what kind of power ratings you are working with.

Or just try nosie filters attached to the back of the speaker lines that connect to your headunit I suppose.